WO2011027816A1 - Power supply circuit and light emission apparatus - Google Patents

Abstract

This invention relates to a power supply circuit for rectifying an AC power and supplying the rectified power to a load and also relates to a light emission apparatus for causing a light emitting diode to emit light, wherein the use of any capacitors having large capacitances is avoided, while the supply of the power to the load can be prevented from being interrupted. There are included: a rectifier circuit for converting an AC power to a pulse wave power; a capacitor; a charging circuit for charging the capacitor; and a combining circuit that is operative to cause the capacitor to discharge the power, charged therein, when a pulse wave power output by the rectifier circuit is equal to or less than a first threshold voltage, and that is further operative to combine the discharged power with the output pulse wave power.

Description

Power supply circuit and light emitting device

The present invention relates to a power supply circuit that rectifies AC power and supplies it to a load, and a light emitting device that emits light from a light emitting diode (LED).

In order to obtain power from commercial AC power and cause the LED to emit light, a rectifier circuit that converts the AC power into power suitable for supplying the LED is required. In such a rectifier circuit, a large-capacity capacitor is required to convert it into clean DC power. An electrolytic capacitor exists as a large-capacity capacitor. However, when this electrolytic capacitor is used, the power factor is reduced and current harmonics are generated. In addition, when the electrolytic capacitor is used for a long time, ESR increases, the electrolyte is dried up, loss increases, and smoke may be generated. In order to avoid this, it is possible to eliminate the electrolytic capacitor and cause the LED to emit light with the pulsating current output from the rectifier circuit. However, in this case, the power to be supplied to the LED is interrupted at a constant cycle, and the LED repeats blinking. Even if it is not so conspicuous when viewed directly by human eyes, for example, lighting with such a blinking LED is performed. When attempting to take a picture of the screen, it may cause another problem such as a picture with a stripe pattern due to the relationship between the blinking cycle of the LED and the sweep speed of the light receiving element of the camera.

Japanese Patent Laid-Open No. 2007-12808 JP 2008-72141 A JP 2010-21433 A Japanese Patent No. 4353667

In view of the above circumstances, the present invention uses a power supply circuit that avoids the interruption of power supply to a load while avoiding the use of a capacitor having a large capacity that requires the use of an electrolytic capacitor, and uses the power supply circuit An object of the present invention is to provide a light emitting device.

The power supply circuit of the present invention that achieves the above object provides:
A rectifier circuit that converts alternating current power into pulse wave power;
A capacitor,
A charging circuit for charging the capacitor;
And a combining circuit that discharges the electric power charged in the capacitor when the pulse wave power is equal to or lower than a first threshold voltage and combines the electric power with the pulse wave power output from the rectifier circuit.

Here, it is preferable that the power supply circuit of the present invention further includes a constant current circuit for making the power supplied to the load connected to the power supply circuit constant.

In the power supply circuit of the present invention, the synthesis circuit is connected between the output side of the rectifier circuit and the capacitor, and is turned on and off between the output side of the rectifier circuit and the capacitor under control. And the input or output of the rectifier circuit is monitored, the first switch element is controlled to be in the OFF state during the period when the output voltage of the rectifier circuit is equal to or higher than the first threshold voltage, and the output voltage of the rectifier circuit is the first threshold voltage. It is preferable to have a discharge control circuit that controls the first switch element to an ON state for a period less than the period.

In this case, it is preferable that the first switch element is a semiconductor switch element, and the charging circuit is equivalent to the semiconductor switch element, and the output side of the rectifier circuit is an anode and the capacitor side is a cathode diode.

In the power supply circuit of the present invention, the charging circuit may be a diode having an anode connected to the output side of the rectifier circuit and a cathode connected to the capacitor side.

Alternatively, in the power supply circuit of the present invention, the charging circuit is connected between the output side of the rectifier circuit and the capacitor, and is turned on and off between the output side of the rectifier circuit and the capacitor under control. And the input or output of the rectifier circuit is monitored, the second switch element is controlled to be in an ON state during a period when the output voltage of the rectifier circuit is equal to or higher than the second threshold voltage, and the output voltage of the rectifier circuit is set to the second threshold voltage. The charge control circuit that controls the second switch element to an off state may be included for a period less than the period.

Specifically, the power supply circuit of the present invention is, for example,
A pair of input terminals for receiving AC power;
A pair of output terminals connected to the load,
The rectifier circuit is connected to the pair of input terminals and the pair of output terminals, converts AC power received at the pair of input terminals into a pulse wave current, and supplies the pulse wave current to the pair of output terminals,
One end of the capacitor is connected to the first output terminal of the pair of output terminals,
A first circuit that is connected between the other end of the capacitor and a second output terminal of the pair of output terminals and that is controlled to turn on and off between the other end and the second output terminal; The switch element and the AC power are monitored, and the switch element is controlled to be in an OFF state during a period in which the voltage as the absolute value of the AC power is not less than the first threshold voltage, and the voltage as the absolute value of the AC power is the first voltage. A period less than the threshold voltage has a discharge control circuit for controlling the first switch element to an ON state;
The charging circuit may be a circuit that charges the capacitor with the output power of the rectifier circuit while the first switch element is in the OFF state.

The light emitting device of the present invention that achieves the above object is
The power supply circuit according to any one of the aspects of the present invention, and a light-emitting diode that emits light when power is supplied from the power supply circuit.

Here, in the power supply circuit of the present invention, the light emitting diode preferably has a plurality of light emitting diode elements sequentially connected in series.

The present invention includes a synthesis circuit that discharges the power charged in the capacitor when the pulse wave power output from the rectifier circuit is less than the first threshold voltage and combines it with the pulse wave power. is there. Therefore, according to the present invention, it is sufficient to use a capacitor having a capacity that does not require the use of an electrolytic capacitor, and a long-life capacitor such as a ceramic capacitor can be used. Moreover, according to this invention, it can avoid that the electric power supplied to load is interrupted periodically.

1 is a circuit block diagram showing a power supply circuit as a first embodiment of the present invention. It is a circuit diagram of the light-emitting device as 2nd Embodiment of this invention. It is a circuit diagram of the light-emitting device as 3rd Embodiment of this invention. It is a schematic diagram which shows a high voltage light emitting diode. It is the figure which showed the waveform of each part of the power supply circuit shown in FIG. It is a circuit diagram of the light-emitting device as 4th Embodiment of this invention. It is a circuit diagram of the light-emitting device of 5th Embodiment of this invention. It is a circuit diagram of the light-emitting device of 6th Embodiment of this invention. It is the figure which showed an example of the constant current element used by 5th, 6th embodiment shown to FIG. 7, FIG. It is the figure which showed the circuit diagram which uses multiple general purpose junction FET in parallel. It is the figure which showed the structure of junction FET used by this embodiment. It is the figure which showed the structure of the power package used by embodiment of FIG. 7, FIG. FIG. 13 is a perspective view of the power package shown in FIG. 12. It is the figure which showed the example of a specification of the characteristic value. It is the figure which showed the item in the case of 3rd Embodiment shown in FIG. 3 on the conditions shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings.

Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a circuit block diagram showing a power supply circuit as a first embodiment of the present invention.

The power supply circuit 10 has a pair of input terminals 11a and 11b and a pair of output terminals 12a and 12b.

As an example, commercial AC power 20 having an effective value of 100 V and 50 Hz is input to the pair of input terminals 11a and 11b. A load 30 is connected to the pair of output terminals 12a and 12b.

The power supply circuit 10 includes a rectifier circuit 13 connected to a pair of input terminals 11a and 11b and a pair of output terminals 12a and 12b. This rectifier circuit 13 is constituted by a combination of diodes 17 and converts the AC power received at the input terminals 11a and 11b into full-wave rectified DC power to supply it to the output terminals 12a and 12b. . The electric power supplied to the output terminals 12a and 12b is supplied to the load 30 via the output terminals 12a and 12b.

Here, in the present embodiment, of the first output terminal 12a and the second output terminal 12b constituting the pair of output terminals 12a and 12b, the first output terminal 12a is connected to the ground line, and the second output terminal 12a is connected to the ground line. The output terminal 12b is supplied with positive voltage power compared to the ground line.

The power supply circuit 10 also has a synthesis circuit composed of a switch element 15 and a control circuit 16. The power supply circuit 10 further includes a capacitor 14 having one end connected to the first output terminal 12a. The switch element 15 is connected between the other end of the capacitor 14 and the second output terminal 12b. Under the control of the control circuit 16, the switch element 15 is turned on / off between the capacitor 14 and the second output terminal 12b. To do.

In addition, the control circuit 16 monitors the AC power input to the rectifier circuit 13, and controls the switch element 15 to be in an OFF state during a period in which the voltage of the AC power is an absolute value or more than a threshold voltage (for example, 30V). During a period in which the voltage (absolute value) of AC power is less than the threshold voltage, the switch element 15 is controlled to be on.

Further, the power supply circuit 10 includes a diode 17 having an anode connected to the second output terminal 12 b and a cathode connected to a connection node between the capacitor 14 and the switch element 15. The diode 17 is an example of a charging circuit according to the present invention, and charges the capacitor 14 with the output power of the rectifier circuit 13 while the switch element 15 is in the OFF state.

According to the power supply circuit 10, when the input voltage of the rectifier circuit 13 is equal to or higher than a threshold value (for example, 30V), the switch element 15 is turned off, and the output power of the rectifier circuit 13 is supplied to the output terminal 12b as it is. The capacitor 14 is supplied to the load 30 and charged through the diode 17.

On the other hand, when the input voltage of the rectifier circuit 13 is less than a threshold value (for example, 30 V), the switch element 15 is turned on, and the electric power accumulated in the capacitor 14 is supplied to the output terminal 12b via the switch element 15. Therefore, the load 30 is always supplied with power having a voltage equal to or higher than the threshold voltage, and it is avoided that the power supply is interrupted. Further, the capacitor 14 only needs to discharge power when it is lower than a threshold voltage (for example, 30 V), and may be a capacitor having a small capacity of, for example, several μF.

FIG. 2 is a circuit diagram of a light-emitting device as a second embodiment of the present invention.

The light emitting device 1A is roughly divided into a power supply circuit 100A and an LED light emitting circuit 300. Among these, a detailed circuit diagram is shown for the power supply circuit 100A which is a characteristic part of the present embodiment, and the LED light emitting circuit 300 is shown in one block.

The power supply circuit 100A constituting the light emitting device 1A has a pair of input terminals 111a and 111b and a pair of output terminals 121a and 121b. As in the case of the embodiment shown in FIG. 1, as an example, commercial AC power 200 having an effective value of 100 V and 50 Hz is input to the pair of input terminals 111a and 111b. Further, an LED light emitting circuit 300 as a load is connected to the pair of output terminals 121a and 121b. The LED light-emitting circuit 300 includes a light-emitting diode (LED) 301 and causes the LED 301 to emit light with power supplied from the power supply circuit 100A.

Further, the power supply circuit 100A includes a rectifier circuit 130 connected to the pair of input terminals 111a and 111b and the pair of output terminals 121a and 121b. The rectifier circuit 130 includes four diodes 131a, 131b, 131c, and 131d that are bridge-connected. The rectifier circuit 130 converts AC power received at the input terminals 111a and 111b into DC pulsating power, and outputs the output via the output terminals 121a and 121b. The LED light emitting circuit 300 is supplied.

Here, also in the present embodiment, as in the embodiment shown in FIG. 1, the first output terminal 121a of the pair of output terminals 121a and 121b is connected to the ground line, and the second output terminal 121b includes When the ground line (first output terminal 121a) is used as a reference, positive voltage power is supplied.

A small-capacitance (for example, 100 nF) capacitor 180 is connected to the output side of the rectifier circuit 130. This is for removing high-frequency noise and is not a capacitor that contributes to smoothing the pulsating flow.

The power supply circuit 100A includes a capacitor 140 having one end connected to the first output terminal 121a. A MOSFET 150 is disposed between the other end of the capacitor 140 and the second output terminal 121b. The MOSFET 150 serves as both a semiconductor switch element and a charging circuit according to the present invention. That is, MOSFET 150 is turned on when an L level voltage is supplied to its gate, and is turned off when an H level voltage is supplied to its gate. As a result, the MOSFET 150 operates as a switching element according to the present invention. The MOSFET 150 has an equivalent diode 170 having an anode on the second output terminal 121b side and a cathode on the capacitor 140 side. The equivalent diode 170 serves as a charging circuit according to the present invention.

Furthermore, the power supply circuit 100A has a control circuit 160. The control circuit 160 is a circuit that forms an example of the synthesis circuit according to the present invention together with the MOSFET 150.

The control circuit 160 includes a diode 161a having an anode connected to the first input terminal 111a, and another diode 161b having an anode connected to the second input terminal 111b and a cathode connected to the cathode of the diode 161a. Have Further, a Zener diode 162 whose cathode is connected to the cathodes of the two diodes 161a and 161b, a resistor 163a connecting between the anode of the Zener diode 162 and the base of the NPN transistor 164a, and the base of the NPN transistor 164a, The resistor 163b is connected to the second output terminal 121a (ground line). Further, the emitter of the NPN transistor 164a is connected to the second output terminal 121a (ground line), the collector is connected to the base of another NPN transistor 164b, and the second output terminal 121b is connected via the resistor 163e. It is connected to the. The emitter of the other NPN transistor 164b is connected to the first output terminal 121a (ground line), and the collector is connected to the gate of the MOSFET 150 via the resistor 163d. The gate of the MOSFET 150 is connected to a connection node between the capacitor 140 and the MOSFET 150 via the resistor 163c.

Here, regardless of whether the instantaneous voltage of the AC power 200 is on the positive side or the negative side, if the threshold voltage determined by the Zener voltage of the Zener diode 162 (for example, ± 30 V) is exceeded, the H level voltage is applied to the base of the NPN transistor 164a. Is applied to make the NPN transistor 164a conductive, whereby the base of the other NPN transistor 164b becomes L level, the gate of the MOSFET 150 becomes H level, and the MOSFET 150 is turned off. Then, the output power of the rectifier circuit 130 is output as it is to the output terminal 121b and supplied to the LED light emitting circuit 300A, and the LED 301 emits light.

At this time, electric power is stored in the capacitor 140 through an equivalent diode 170.

On the other hand, when the voltage of the AC power 200 is less than the threshold voltage (for example, 30 V), the voltage cannot pass through the Zener diode 162, and the base of the NPN transistor 164a is supplied via the resistor 163b. Becomes ground potential (L level). Therefore, the NPN transistor 164a is turned off, and a voltage of H level is applied to the base of the other NPN transistor 164b via the resistor 163e, so that the NPN transistor 164b is turned on. Becomes L level, and the MOSFET also becomes conductive (ON state).

Then, the power charged in the capacitor 140 is supplied to the second output terminal 121b via the MOSFET 150. Thereby, the voltage of the second output terminal 121b remains at a voltage of about the threshold voltage (for example, 30V) and does not decrease below that, and the light emission of the LED 301 is continued by the power. The capacitor 140 discharges power only when it is lower than a threshold voltage (for example, 30 V), and may be a capacitor having a small capacity of about 4.7 microfarads, for example. Therefore, a long-life ceramic capacitor or the like can be used.

Here, the LED light emitting circuit 300 can be sufficiently devised such as adding a current limiting element (such as a constant current diode) or stabilizing the brightness by combining a temperature detection sensor or an illuminance detection sensor.

FIG. 3 is a circuit diagram of a light emitting device as a third embodiment of the present invention.

The light emitting device 1B is roughly divided into a power supply circuit 100B and a high voltage light emitting diode 500. Among these, the power supply circuit 100B is shown in a detailed circuit diagram, and the high voltage light emitting diode 500 is shown in a simplified manner in FIG. The structure of the high voltage light emitting diode 500 will be described later.

The power supply circuit 100B includes a fuse 401, a rectifier circuit 410, a high voltage hold circuit 420, a waveform synthesis circuit 430, a switching power supply 440, a constant current circuit 470, and a smoothing capacitor 481.

The rectifier circuit 410 corresponds to an example of a rectifier circuit according to the present invention, and the high voltage hold circuit 420 corresponds to an example of both a capacitor and a charging circuit according to the present invention. The waveform synthesis circuit 430 corresponds to a part of the synthesis circuit referred to in the present invention. The remaining part of the synthesis circuit according to the present invention is included in the switching power supply 440. Details will be described later. The switching power supply 440 includes a current adjusting switching circuit for adjusting the current flowing through the LED light emitting circuit 300B, and an internal power supply circuit, in addition to the components of the combining circuit, as well as the constant current circuit 470.

The smoothing capacitor 481 is a capacitor that is responsible for smoothing the output voltage of the switching power supply 440. Since the driving current of the high voltage light emitting diode 300 can be small, a film capacitor or a ceramic capacitor can be used as the smoothing capacitor 481.

The rectifier circuit 410 is composed of four diodes 411 to 414 connected in a bridge, and converts commercial AC power having an effective value of 100 V into DC pulse wave power.

The high-voltage hold circuit 420 includes a capacitor 421 whose one end is grounded, and a diode whose anode is connected to the output of the rectifier circuit 410 for charging the capacitor 421 and whose cathode is connected to the other end of the capacitor 421. 422. The diode 422 is an example of a charging circuit according to the present invention. As with the smoothing capacitor 481, a film capacitor or a ceramic capacitor can be used for the capacitor 421.

The waveform synthesis circuit 430 also includes a diode 431 having an anode connected to the output of the rectifier circuit 410 and a cathode connected to the switching power supply 440, a P-channel MOS transistor 432 connecting the capacitor 421 and the cathode of the diode 431, A resistor 433 having one end connected to the gate of the P-channel MOS transistor 432 and the other end connected to the switching power supply 440, and a resistor connecting the connection node between the capacitor 421 and the diode 422 and the gate of the P-channel MOS transistor 432 434.

Further, the switching power supply 440 includes a resistor 441, a P-channel MOS transistor 442 that connects the output of the waveform synthesis circuit 430 (that is, a connection node between the diode 431 and the P-channel MOS transistor 432) and the resistor 441, and its P-channel MOS. A resistor 443 connecting between the gate of the transistor 442 and the output of the waveform synthesis circuit 430, another resistor 444 having one end connected to the gate of the P-channel MOS transistor 442, and the resistor 444 and the ground line N-channel MOS transistor 445 connecting between the two. The gate of this N channel MOS transistor 445 is connected to the output of a comparator 446 described later. The P-channel MOS transistor 442, the N-channel MOS transistor 445, and the two resistors 443 and 444 transmit the output power of the waveform synthesis circuit 430 to the LED light-emitting circuit 300B while switching in accordance with the change in the output of the comparator 446. A switching circuit is configured. This switching circuit, together with the comparator 446 and the like, constitutes a current adjustment circuit that adjusts the supply current to the high voltage light emitting diode 500.

The switching power supply 440 includes a Zener diode 447 whose anode is grounded, a capacitor 448 connecting the anode and cathode of the Zener diode 447 in parallel with the Zener diode 447, an output of the waveform synthesis circuit 430, and its And a resistor 449 connecting the cathode of the Zener diode 447.

The zener diode 447, the capacitor 448, and the resistor 449 constitute an internal power supply circuit that generates constant voltage → power used in the switching power supply 440 and the constant current circuit 470. Here, as an example, electric power of an internal power supply Vcc = 5.0 volts is generated and supplied to the comparator 446, another comparator 450, and the constant current circuit 470.

The positive power source of the comparator 450 is connected to the internal power source Vcc, and the negative power source is grounded. Two resistors 451 and 452 connected in series with each other are arranged between the internal power supply Vcc and the ground line, and the first reference voltage Vref1 is generated by these two resistors 451 and 452. . The connection node of these two resistors 451 and 452 is connected to the negative input terminal of the comparator 450, and supplies the first reference voltage Vref1 to this negative input terminal. In addition, two resistors 453 and 454 connected in series with each other are arranged between the output of the rectifier circuit 410 and the ground line, and the positive input terminal of the comparator 450 is connected to the two resistors 453 and 454. Connected to the node. That is, the pulsating voltage generated by the rectifier circuit 410 is divided and input to the positive input terminal. Further, the output terminal of the comparator 450 is connected to a resistor 433 constituting the waveform synthesis circuit 430. Here, since the commercial AC power supply 200 of 100 volts is connected, the rectifier circuit 410 generates pulse wave power having a pulse wave voltage with a peak of 141 volts. The pulse wave voltage is divided and inputted to the positive input terminal of the comparator 450. When the divided pulse wave voltage is higher than the reference voltage Vref1, the output voltage of the comparator 450 becomes H level. The P channel MOS transistor 432 of the waveform synthesis circuit 430 is cut off. On the other hand, when the divided pulsating voltage input to the positive input terminal of the comparator 450 is lower than the reference voltage Vref1, the output of the comparator 450 becomes L level and the P channel MOS transistor 432 is made conductive. . In this embodiment, the output of the comparator 450 is H level when the voltage of the pulse wave power, which is the output of the rectifier circuit 410, is 100 volts or higher, and the resistors 451 to 454 so as to be L level when the voltage is 100 volts or lower. The resistance value is adjusted. Thus, the capacitor 421 of the high voltage hold circuit 420 is charged via the diode 422 when the voltage of the pulse wave power that is the output of the rectifier circuit 410 is 100 volts or more in this embodiment, and the voltage of the pulse wave power is When it becomes 100 volts or less, it is discharged through the P-channel MOS transistor 432.

Next, the description of the internal configuration of the switching power supply 440 is temporarily interrupted, and the configuration of the constant current circuit 470 will be described first.

The constant current circuit 470 includes a resistor 471 having one end connected to the internal power supply Vcc, a first N-channel MOS transistor 472 connecting the other end of the resistor 471 and the ground line, and a high voltage light emitting diode. 500 has a second N-channel MOS transistor 471 disposed between the cathode side of 500 and the ground line.

The gates of these two N-channel MOS transistors 472 and 473 are connected to each other.

The gates and connection nodes of the resistor 471 and the first N-channel MOS transistor 472 are connected to each other.

Here, it returns to the description of the switching power supply 440 again.

The positive power source of the comparator 446 constituting the switching power source 440 is connected to the internal power source Vcc, and the negative power source is grounded. Further, two resistors 455 and 456 connected in series with each other are arranged between the internal power supply Vcc and the ground line to generate the second reference voltage Vref2. A connection note between these two resistors 455 and 456 is connected to the plus input terminal of the comparator 446 and supplies the second reference voltage Vref2 to the plus input terminal.

The negative input terminal of the comparator 446 is connected to the connection node between the cathode side of the high-voltage light emitting diode 500 and the second N-channel MOS transistor 473 constituting the constant current circuit 470, and the voltage Vi of the connection node is supplied. Has been. Further, the output terminal and the positive input terminal of the comparator 446 are connected via another resistor 457.

The description of the power supply circuit 100B shown in FIG. 3 is temporarily interrupted, and FIGS. 4 and 5 are described first.

FIG. 4 is a schematic diagram showing a high voltage light emitting diode.

The high voltage light emitting diode 500 corresponds to an example of the light emitting diode according to the present invention. Here, the high voltage light emitting diode 500 is composed of 20 optical microcells 510 connected in series between the P-type terminal 520 and the N-type terminal 530. These optical microcells 510 are an example of a light emitting diode element according to the present invention. Each of these optical microcells 510 is a light emitting element, and in this case, the driving voltage is 4.5 volts. Therefore, the driving voltage Vd of the high voltage light emitting diode 500 is 90 volts (4.5 volts × 20 = 90 volts), which is a series of 20 light emitting elements. As the drive current, a drive current for driving one light emitting element is sufficient. Therefore, the drive current can be reduced to 1/20 compared to the case where these light emitting elements are connected in parallel.

In FIG. 3 and each figure described later, a high voltage light emitting diode 500 having the structure of FIG. 4A is shown in FIG.

FIG. 5 is a diagram showing waveforms of respective parts of the power supply circuit 100B shown in FIG.

5A shows the signal waveform of the input voltage signal of the rectifier circuit 410 shown in FIG. 3, that is, the A waveform (solid line) that is the waveform of the commercial AC power supply 200, and the B waveform (broken line) that is the waveform of the opposite phase. Is shown.

FIG. 5B shows an output voltage waveform of the rectifier circuit 410. This output voltage waveform is the higher voltage on the positive voltage side of both the A waveform and the B waveform shown in FIG.

FIG. 5C is a diagram showing an output voltage waveform of the waveform synthesis circuit 430. Here, the output of the high voltage hold circuit 420 is a charge in a peak period (herein, abbreviated as “peak voltage”) of, for example, 100 volts or more of the output voltage of the rectifier circuit 410, and the peak The discharge through the P-channel MOS transistor 432 in the voltage period other than the voltage is repeated. The timing at which the P-channel MOS transistor 432 is turned on / off is set by the ratio of the resistance values of the resistors 451 and 452 of the comparator 450 and the ratio of the resistance values of the resistors 453 and 454. Here, it is set to 100 volts as described above. The output voltage of the waveform synthesis circuit 430 shown in FIG. 5C is the higher voltage of the output voltage of the rectifier circuit 410 and the charging voltage of the capacitor 421 of the high voltage hold circuit 420. This voltage waveform pulsates between Vmax and Vmin according to a trigonometric function and a constant current discharge function. It is a known fact that Vmax is 141 volts when the commercial power source is 100 volts AC. Vmin is determined by the on-timing of the MOS switch, and in this case is 100 volts.

The output of the waveform synthesizing circuit 430 shown in FIG. 5C is applied to the high voltage light emitting diode 500 and the constant current circuit 470 connected in series via the switching power supply 440. The voltage applied to the high voltage light emitting diode 500 and the constant current circuit 470 is divided into the drive voltage Vd (90 V) of the high voltage light emitting diode 300 and the Vf of the N channel MOS transistors 472 and 473 constituting the constant current circuit 470 (about. 5V), that is, Vd + Vf or higher, the high voltage light emitting diode 500 can emit light stably.

Thus, when Vmin is always larger than Vd + Vf, the light emitting diode is always lit. When Vmin is smaller than Vd + Vf, the light emitting diode blinks at a frequency twice the AC frequency of the commercial power supply. This is not a problem in terms of illumination, but is generally undesirable because it causes flickering in synchronism with the driving cycle of an electronic camera or the like, resulting in many disadvantages in practical use.

As shown in FIG. 5C, in the case of AC 50 Hz, one cycle is 20 milliseconds, and the output waveform pulsates at its quarter cycle, 200 Hz, but the light-emitting diode is stable and static. Flashes. Light intensity is easily adjusted by driving the entire high-voltage light emitting diode at a frequency higher than this pulsation frequency and changing the duty ratio at a high frequency that does not affect other devices when dimming is required. be able to.

In the case of the power supply circuit 100B shown in FIG. 3, the switching power supply 440 is operated so that the drive voltage of the constant current circuit 470 becomes the minimum voltage necessary for constant current operation. In this case, the constant voltage drive voltage, that is, the voltage Vi at the connection node between the second N-channel MOS transistor 473 and the high voltage light emitting diode 500 constituting the constant current circuit 470 is 1.5 ± 0.5 volts. It is set to work. For this purpose, the Vref2 voltage of the comparator 446 is configured to have a hysteresis of 1 volt centered on 1.5 volts. When Vi is higher or higher than 2 volts, the N-channel MOS transistor 445 is turned off to turn off the P-channel MOS transistor 442 for power supply, and the power supply to the high voltage light emitting diode 500 is stopped. As a result, the high voltage light emitting diode 500 is supplied with electric power due to the discharge of the accumulated charge in the smoothing capacitor 481. As the smoothing capacitor 481 is discharged, the voltage Vo of the smoothing capacitor 481 and the voltage Vi of the constant current circuit 470 are reduced, and when the voltage Vi drops below 1 volt, the N-channel MOS transistor 445 is turned on. The P-channel MOS transistor 442 is turned on, and the power supply to the high voltage light emitting diode 500 and the charging to the smoothing capacitor 481 are started via the current limiting resistor 441.

Here, let Toff be the period during which the P-channel MOS transistor 442 is off. When P channel MOS transistor 442 is turned on, Vo and Vi rise, and when Vi becomes 2 volts, P channel MOS transistor 442 is turned off again. A period during which the P-channel MOS transistor 442 is on is assumed to be Ton.

The period of Toff + Ton is one cycle. The main factors that determine Toff are the amplitude of the Vi voltage, the capacity of the smoothing capacitor 481, and the drive current value. In this case, 10 microseconds is set. The amplitude of the Vi voltage is determined by the hysteresis voltage of the reference voltage Vref2 of the comparator 446. In this example, the voltage is ± 1 volt centered on 1.5 volts and the hysteresis voltage width is 1 volt. The voltage of Vref2 is easily determined by the ratio of the resistance values of the resistors 455, 456, and 457. The factor that determines Ton is the voltage difference between the source voltage of the P-channel MOS transistor 442, that is, the output voltage of the waveform synthesis circuit 430, and the voltage Vo of the smoothing capacitor 481, and the current limiting resistor 441 in series with the P-channel MOS transistor 442. It depends on the resistance value and the drive current. The source voltage, that is, the output voltage of the waveform synthesis circuit 430 is a smoothed voltage output as shown in FIG. 5C, and when the commercial AC power supply 200 is AC 100 volts, the maximum is 141 volts and the minimum is 100. It is a bolt. Therefore, Ton varies periodically according to the AC cycle. A 50 Hz alternating current has an irregular period of 200 Hz. In this way, the Ton time changes from about 0.5 microseconds to about 5 microseconds. In this way, the cycle Toff + Ton of the switching power supply 440 is not constant and varies greatly depending on Ton. This change is a function of the switching power supply. In this case, the period is changed from 1.5 microseconds to 15 microseconds, the frequency is changed from about 100 KHz to about 60 KHz, and the voltage oscillation width of Vi is set to about 1 volt. The Vo voltage oscillates at Vd (drive voltage of the high voltage light emitting diode) + 1.5 ± 1 volts.

In this way, Vi is controlled with an amplitude of about 1 volt at the center of 1.5 volts, and heat loss in the constant current circuit can be minimized. The heat loss is very small at 75 milliwatts at 50 milliamperes × 1.5 volts, and the heat loss is negligible compared to the power consumption in the light emitting diode. Further, if such high-speed switching is performed, the smoothing capacitor 481 may be 0.5 microfarad or less, so that a film capacitor or a ceramic capacitor with no limit in the life can be used. It is an extremely efficient switching power supply circuit.

Supplementary explanation of the operation of the constant current circuit 470 and the comparator 446 in FIG. The constant current circuit 470 can easily determine its characteristics by the ratio of the sizes of the N-channel MOS transistors 472 and 473 constituting the current mirror circuit and the resistance value of the resistor 471. The internal power supply Vcc that determines the power supply of the comparator 446 and the reference voltage Vref2 is 5 volts with a simple power supply circuit.

In the circuit configuration of FIG. 3, the diodes 411 to 414 of the rectifier circuit 410, the diode 422 of the high voltage hold circuit 420, the diode 431 of the waveform synthesis circuit 430, the P-channel MOS transistor 432, and the constant current circuit 470 need only have a low current. Therefore, a one-chip integrated circuit can be easily obtained. Thereby, the miniaturization of the drive module can be realized, and the drive module can be accommodated within the diameters of the bulb caps E26 and E17. Such a circuit can be made into one chip in any case and other circuits can be easily made into a single chip by the insulated power semiconductor technology because the drive current is small.

In FIG. 3, a constant current circuit using a MOS transistor as an example and a switching power supply using a capacitor are shown as examples. However, a circuit that employs an efficient switching circuit using an inductance can also be easily configured. In any circuit configuration, since the drive current is small, the circuit can be simplified and downsized.

FIG. 6 is a circuit diagram of a light-emitting device as a fourth embodiment of the present invention.

Here, the same components as those of the light emitting device of the third embodiment illustrated in FIG. 3 are denoted by the same reference numerals as those illustrated in FIG. 3, and only differences will be described.

The power supply circuit 100C of the light emitting device 1C according to the fourth embodiment shown in FIG. 6 includes a high voltage hold circuit that replaces the high voltage hold circuit 420, the waveform synthesis circuit 430, and the switching power supply 440 in the third embodiment shown in FIG. A circuit 480, a waveform synthesis circuit 490, and a switching power supply 700 are provided.

The high voltage hold circuit 480 of the fourth embodiment shown in FIG. 6 has a P-channel MOS transistor 481 instead of the diode 422 in the third embodiment shown in FIG. The P-channel MOS transistor 481 connects the output of the rectifier circuit 410 and the capacitor 421, and the gate is connected to the output of another comparator 701 incorporated in the switching power supply 700.

Further, the waveform synthesis circuit 490 of the fourth embodiment shown in FIG. 6 has a P-channel MOS transistor 491 and an inverter 492 instead of the diode 431 in the third embodiment shown in FIG. The P channel MOS transistor 491 connects the output of the rectifier circuit 410 and the source of the P channel MOS transistor 442 constituting the switching power supply 700. The inverter 492 has an input connected to the output of the comparator 450 and an output connected to the gate of the P-channel MOS transistor 491.

Further, the switching power supply 700 has a structure in which a comparator 701 and four resistors 702 to 705 are added to the switching power supply 440 in the third embodiment shown in FIG. Two of the four resistors 702 to 705 are connected in series, the resistor 702 is connected to the internal power supply Vcc, the resistor 703 is grounded, and the third reference voltage Vref3 is generated. A node where the two resistors 702 and 703 are connected to each other is connected to the plus input terminal of the comparator 701, and the third reference voltage Vref3 is supplied to the plus input terminal.

The remaining two resistors 704 and 705 are also connected to each other and connect the output of the rectifier circuit 410 and the ground line. A node where the two resistors 704 and 705 are connected to each other is connected to the negative input terminal of the comparator 701.

As a result, when the output voltage of the rectifier circuit 410 is high, the output T2 of the comparator 701 becomes L level and the P-channel MOS transistor 482 becomes conductive, the output of the rectifier circuit 410 and the capacitor 421 are connected, and the capacitor 421 is connected. Charged. When the output voltage of rectifier circuit 410 is low, comparator T2 is at H level, P-channel MOS transistor 482 is turned off, and the output of rectifier circuit 410 and capacitor 421 are disconnected.

When the output voltage of rectifier circuit 410 is high, output T1 of comparator 450 is at H level, P channel MOS transistor 432 is turned off, and capacitor 421 is prevented from discharging, and P channel MOS transistor 491 is discharged. Is turned on, and the output of the rectifier circuit 410 is transmitted to the high voltage light emitting diode 500 via the switching power supply 700. On the other hand, when the output voltage of rectifier circuit 410 is low, the output of comparator 450 becomes L level, P channel MOS transistor 432 is turned on, capacitor 421 is discharged, and P channel MOS transistor 491 is turned off. As a result, the output of the rectifier circuit 410 is cut off.

Here, in the case of the fourth embodiment, the timing of transition between the H level and the L level of T1 and T2 can be set independently, so that the timing of charging and discharging of the capacitor 421 can be adjusted to more optimal timing. It becomes possible.

FIG. 7 is a circuit diagram of a light emitting device according to a fifth embodiment of the present invention.

In the power supply circuit 100D constituting the light emitting device 1D of the fifth embodiment, when compared with the third embodiment of FIG. 3, the switching power supply 440 is omitted and the output of the waveform synthesis circuit 430 is directly applied to the high voltage light emitting diode 500. It has the structure connected to.

In the case of the fifth embodiment shown in FIG. 7, a simple constant current element 601 instead of the constant current circuit 470 is arranged in FIG.

Furthermore, in the case of the fifth embodiment of FIG. 7, the resistor 433 connects the gate of the P-channel MOS transistor 432 and the output of the rectifier circuit 410.

FIG. 8 is a circuit diagram of the light emitting device according to the sixth embodiment of the present invention.

The power supply circuit 100E constituting the light emitting device 1E of the sixth embodiment shown in FIG. 8 has a waveform including the P-channel MOS transistor 432 of the fifth embodiment of FIG. 7 when compared with the fifth embodiment of FIG. Instead of the synthesis circuit 430, a waveform synthesis circuit 590 including a PNP transistor is provided. The emitter of the PNP transistor 511 is connected to the capacitor 421, and the collector is connected to the cathode of the diode 431. The base of the PNP transistor 451 is connected to a connection node between the two resistors 433 and 434.

The resistor 433 connects the base of the PNP transistor 511 and the output of the rectifier circuit 410.

FIG. 9 is a diagram showing an example of a constant current element used in the fifth and sixth embodiments shown in FIGS.

In the case of a 4.5 watt light emitting diode, if a 4.5 volt light emitting diode element having a driving voltage is connected in parallel to each other, a driving current of 1 ampere is required. In the case of the diode 500, the drive voltage Vd is 90 volts, and the drive current is as small as 50 mA of 1/20.

こ の If the drive current is small in this way, a constant current element can be used instead of the constant current circuit. FIG. 9 shows a circuit diagram of the junction FET. It is known that a constant current can be obtained between the drain and the source by connecting the gate of the FET having a negative threshold voltage to the source. A constant current characteristic is obtained at an applied voltage Vf or higher which becomes a constant current (see Patent Document 2 and Non-Patent Document 1). Vf is usually a small value of about 1 volt or less. FIG. 10 shows the voltage-current characteristics. The direction in which the applied voltage is positive is determined by the threshold voltage, electron mobility, and element size. For the direction in which the applied voltage is negative, the diode has a forward current characteristic due to the parasitic diode inside the element. In addition, the device size of this junction FET is a small silicon element of about 0.5mm x 0.5mm, and it is common to take the drain from the front and the source and gate from the back, and this is sealed in a general-purpose mold package. Has been.

The junction FET type constant current circuit is sealed in a small general-purpose diode package, and has a practical driving capacity of about 10 milliamperes. However, the light emitting diode used for illumination requires about 5 watts, and the drive current needs about 50 milliamperes. For this reason, it is necessary to use a plurality of general-purpose package products. Further, the constant current value of the junction FET has two problems, that is, the constant current value usually varies by about 10% due to the variation in the manufacturing process and the constant current value changes due to heat generation due to the large temperature coefficient. When using a plurality, it is possible to reduce the total tolerance by selecting current values and combining them. However, it is complicated to select and use them in the finished CRD.

FIG. 11 shows the structure of the junction FET used in this embodiment in which the poorness of this characteristic is improved. FIG. 11 shows a circuit diagram in which a plurality of general-purpose junction FETs are used in parallel. The junction FET shown in FIG. 11 has a configuration in which four elements are arranged in each of the drain 1 and the drain 2. FIG. 12 shows the structure of the power package 900 used in the embodiment of FIGS. 12A is a plan view and FIG. 12B is a side view. Reference numerals 901 and 906 denote a drain 1 terminal, and reference numerals 903 and 904 denote a drain 2 terminal. The drain 1 and the drain 2 are connected and used at the time of mounting. Reference numerals 902 and 905 denote source / gate electrodes. This power package 900 has a heat sink 907 and has a low thermal resistance of 20 ° C./W. Fig. 13 is a perspective view showing a state in which the junction FET 908 has eight elements, that is, eight elements a, b, c, (1, e, f, g, h) are mounted. In order to obtain this, a constant current value of 6.25 mA is used for each element, which is a drain electrode with a bonding pad formed on the front surface, and a back electrode which is a common electrode for the source and drain and is connected to the substrate. All elements are die-bonded to the source / gate electrodes 902 and 905, and the source / gate of all elements are connected to the source / gate electrodes 902 and 905 through the substrate of each element. The drains of the elements a, b, c, and d are connected to the drain 1 terminals 901 and 906 by wire bonds, and the drains of the elements e, f, g, and h are drained. The two terminals 903 and 904 are connected by wire bonding, and the drain 1 terminals 901 and 906 and the drain 2 terminals 903 and 904 are connected on the mounting substrate, thereby a, b, c, d, e, f, g, The drains of 8 elements of h are connected to one, these elements are small silicon elements of 0.3 mm × 0.3 mm meter, and when the elements are die-bonded from the wafer, the constant current values of the individual elements are preset. It is possible to mount a combination of elements so that the required total constant current value is obtained by measuring, and by combining elements whose characteristics are known on the wafer in this way, the tolerance between elements is 10%. Even if there is a variation of 8%, it is possible to easily make a tolerance of 1% with the combination of 8. At the stage of use, it is as if a high-precision junction FE. T can be realized.

By using a package having a low thermal resistance as shown in FIG. 12 and dividing the FET element, the heat transfer from the element to the lead frame can be dispersed, the thermal resistance to the heat sink can be divided, and the temperature rise of the element is suppressed. be able to. Thus, by adopting a multi-chip mounting system as a constant current element, many merits such as a reduction in tolerance and a reduction in thermal resistance can be created. In this way, the junction FET type constant current element used in the present embodiment simultaneously compensates for the weak point that the characteristic tolerance is large and the weak point that the temperature dependency is large.

The characteristics of the junction FET type constant current device used in FIGS. 7 and 8 as in this example are 50 mA current drive, 1.5 watt heat generation with an average voltage drop of 30 volts, and a 20 ° C./watt package. The temperature rise at can be suppressed to about 30 ° C. If it is this level, the temperature coefficient of a constant current will not become a big problem practically.

7 and 8 are examples of using a simple constant current element without using a switching power supply, and the operation will be described below by taking FIG. 7 as an example. When the gate voltage of the P-channel MOS transistor 432 falls below the threshold voltage Vt in the waveform synthesis circuit 430 of FIG. 7, the P-channel MOS transistor 432 is turned on. That is, when the output voltage of the rectifier circuit 410 decreases by a certain value or more from the charging voltage of the capacitor 421, it is turned on and current is supplied from the high voltage hold circuit 420. That is, when the output voltage of the rectifier circuit is low, the P-channel MOS transistor 432 is turned on, current is supplied from the high-voltage hold circuit 420 to the high-voltage light emitting diode 500, and when the output voltage of the rectifier circuit 410 increases, the P-channel MOS transistor The transistor 432 is turned off and starts to charge the capacitor 421 with a high voltage, and current supply from the waveform synthesis circuit 430 is performed through the diode 431. In this manner, the light emitting diode drive voltage has a waveform output as shown in FIG.

FIG. 8 shows an example in which a PNP transistor 511 is used instead of the P-channel MOS transistor 432 in FIG. Since the operation is the same, the description is omitted.

Next, an example of design values of application examples of the present invention will be shown. FIG. 14 shows a specification example of the characteristic value. The commercial power supply is 100 VAC, the frequency of the power supply is 50 Hz, the applied voltage of the light emitting diode is 90 volts, and the light emitting diode is formed by 20 stages of 4.5 volt driving elements in series. The driving constant current value is 50 milliamperes, and the power consumption is 4.5 watts.

FIG. 15 shows specifications in the case of the third embodiment shown in FIG. 3 under the conditions shown in FIG. Light emitting diode heat generation is 4.5 watts, and constant current element heat generation is about 1 watt. The thermal resistance of the light emitting diode package is 5 ° C./W, the device temperature is as low as 22.5 ° C. with respect to the ambient temperature, the thermal resistance of the constant current device is 20 ° C./W, and the device temperature is the ambient temperature. On the other hand, the temperature rise is as low as 30 ° C., and it can be stably used as a light emitting system using a commercial power source.

In the case of the third embodiment using a switching power supply (see FIG. 3), the heat loss of the constant current portion is as extremely small as 75 milliwatts. Therefore, the overall efficiency of the light emitting device 1B can be improved. Whether the configuration shown in FIGS. 3 and 6 or the configuration shown in FIGS. 7 and 8 is adopted depends on the purpose in terms of cost, size, and efficiency.

In this example, 100 volts is used as the commercial power supply, but the same configuration can be used for commercial power supplies of other voltages. For example, for 200 volts, a light-emitting diode having a 180-volt specification can be realized by changing the number of optical microcells of the light-emitting diode from 20 to 40, and a similar effect can be created by using this.

¡Applications of light emitting diodes are expanding for energy saving. According to the present invention, the fact that the driving circuit can be simplified and miniaturized by using a high-voltage driven light emitting diode further promotes the popularization of the light emitting diode for energy saving of the lighting fixture in the future. In particular, the practical use of low-power consumption, small-sized and long-life light-emitting sources is extremely important in applications where light bulbs are used in closed spaces where importance is placed on the replacement of small-sized light bulbs that support E17 caps and the design of lighting equipment. It is what you have.

1B, 1C, 1D, 1E Light-emitting device 10, 100A, 100B, 100C, 100D, 100E Power supply circuit 11a, 11b, 111a, 111b Input terminal 12a, 12b, 121a, 121b Output terminal 13, 130, 410 Rectifier circuit 14,140 , 180, 421, 448, 481 Capacitor 15 Switch element 16, 160 Control circuit 131a, 131b, 131c, 131d, 17, 161a, 161b, 411 to 414, 422, 431 Diode 30 Load 150 MOSFET
162, 447 Zener diode 163a, 163b, 163c, 163d, 433, 434, 443, 444, 449, 451, 452, 453, 454, 455, 456, 457, 471 Resistor 164a, 164b NPN transistor 170 Equivalent diode 200 Commercial AC power supply 300 LED light emitting circuit 301 Light emitting diode (LED)
401 Fuse 420, 480 High voltage hold circuit 430, 490, 590 Waveform synthesis circuit 432, 442, 482, 491 P channel MOS transistor 440, 700 Switching power supply 441 Current limiting resistor 445, 472, 473 N channel MOS transistor 446, 450 , 701 Comparator 470 Constant current circuit 481 Smoothing capacitor 500 High voltage light emitting diode 510 Optical microcell 511 PNP transistor 520 P type terminal 530 N type terminal 900 Power package 901, 906 Drain 1 terminal 902, 905 Source / Gate electrode 903, 904 Drain 2-terminal 907 heat sink 908 junction FET

Claims (9)

A rectifier circuit that converts alternating current power into pulse wave power;
A capacitor,
A charging circuit for charging the capacitor;
A power supply comprising: a combining circuit that discharges the electric power charged in the capacitor when the pulse wave power is equal to or lower than a first threshold voltage and combines the electric power with the pulse wave power output from the rectifier circuit circuit. 2. The power supply circuit according to claim 1, further comprising a constant current circuit for making a supply current to a load connected to the power supply circuit a constant current. The synthesis circuit is
A first switch element connected between the output side of the rectifier circuit and the capacitor, and under control to turn on and off between the output side of the rectifier circuit and the capacitor;
The input or output of the rectifier circuit is monitored, and the first switch element is controlled to be in an off state during a period when the output voltage of the rectifier circuit is equal to or higher than the first threshold voltage, and the output voltage of the rectifier circuit is 3. The power supply circuit according to claim 1, further comprising a discharge control circuit that controls the first switch element to be in an ON state during a period of less than one threshold voltage. The first switch element is a semiconductor switch element, and the charging circuit is formed equivalently to the semiconductor switch element, and the output side of the rectifier circuit is an anode and the capacitor side is a cathode diode. The power supply circuit according to claim 3. The power supply circuit according to any one of claims 1 to 4, wherein the charging circuit is a diode having an anode connected to the output side of the rectifier circuit and a cathode connected to the capacitor side. The charging circuit is
A second switching element connected between the output side of the rectifier circuit and the capacitor, and under control to turn on and off between the output side of the rectifier circuit and the capacitor;
The input or output of the rectifier circuit is monitored, the second switch element is controlled to be in an ON state during a period when the output voltage of the rectifier circuit is equal to or higher than a second threshold voltage, and the output voltage of the rectifier circuit is 5. The power supply circuit according to claim 1, further comprising: a charge control circuit configured to control the second switch element to an off state during a period of less than a threshold voltage. A pair of input terminals for receiving AC power;
A pair of output terminals connected to the load,
The rectifier circuit is connected to the pair of input terminals and the pair of output terminals, converts AC power received at the pair of input terminals into a pulse wave current, and supplies the pulse wave current to the pair of output terminals,
The capacitor has one end connected to a first output terminal of the pair of output terminals,
The synthesis circuit is connected between the other end of the capacitor and a second output terminal of the pair of output terminals, and is turned on / off between the other end and the second output terminal under control. A first switch element that monitors the AC power, and controls the switch element to be in an OFF state during a period in which the voltage as the absolute value of the AC power is equal to or higher than the first threshold voltage. A discharge control circuit for controlling the first switch element to an ON state during a period in which the voltage as a value is less than the first threshold voltage,
The power supply circuit according to claim 1, wherein the charging circuit is a circuit that charges the capacitor with output power of the rectifier circuit while the first switch element is in an OFF state. A power supply circuit according to any one of claims 1 to 7,
A light-emitting device comprising: a light-emitting diode that emits light upon receiving power from the power supply circuit. The light emitting device according to claim 8, wherein the light emitting diode has a plurality of light emitting diode elements sequentially connected in series.

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